Fix possible notice when comparing goal data #18355

Description:

happened as some metrics might have been formatted twice

fixes #18261

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

@sgiehl this makes sense :+1:, but I would expect this might happen in other contexts too. Basically any context where an API call results in more API calls to the Goals.get method. Eg, pivoting might also have this problem. I suppose a generic fix is out of scope at this point.